EPA failed to act on revisions to pH, Dissolved Oxygen, and Ammonia Assessment Methods
Yesterday, Upper Missouri Waterkeeper and the Montana Environmental Information Center (MEIC) filed a 60-day Notice of Intent to Sue the Environmental Protection Agency (EPA) for its failure to approve or disapprove revisions to Montana’s water quality standards – specifically new assessment methodologies for pH, dissolved oxygen, and ammonia – within the mandatory timeline under the federal Clean Water Act. These methodologies effectively alter the magnitude, duration, and frequency of applicable water quality standards, necessitating federal oversight that has yet to occur.
“Both the State of Montana and the federal government are making purposeful choices to reduce transparency and reject the preventative approach for water pollution control – all to protect special interests while sacrificing our economy, environment, wildlife, and communities that all rely on clean water,” said Guy Alsentzer, Executive Director of Upper Missouri Waterkeeper. “The EPA’s silence in the face of these de facto revisions is a violation of the Clean Water Act and an abandonment of the precautionary approach required to protect Montana’s waterways and finite water resources from pollution and degradation.”
“Protection of clean water is a primary responsibility of the EPA, but instead it is letting Montana weaken our water quality standards and degrade our water,” stated Derf Johnson, Deputy Director of the Montana Environmental Information Center. “It’s no surprise, considering the people in charge, but nonetheless disappointing as clean water is absolutely critical for Montana’s environment and economy.”
This notice of a forthcoming legal challenge centers on the Montana Department of Environmental Quality’s (DEQ) recent implementation of new “assessment methodologies” for pH, dissolved oxygen, and ammonia. Under the Clean Water Act, any revision to a state water quality standard must be submitted to the EPA for review. The EPA has a mandatory duty to act, by approving or denying such revisions, within 30-60 days. DEQ admitted in its June 12, 2026, cover letter for the 2022-2024 Water Quality Integrated Report that it has finalized and begun applying these new protocols, yet the EPA has taken no formal action to approve or disapprove them.
These assessment methodologies act as de facto narrative water quality standards for nutrient pollutants. For years, Montana led the nation with science-based numeric nutrient water quality standards. However, following the legislative repeal of these standards via House Bill 664 in the 2025 Session, the State has moved toward a narrative approach, despite lacking a defensible implementation framework. These new protocols for pH, DO, and ammonia effectively weaken impairment thresholds, allowing degraded waterways to escape necessary pollution clean up plans or TMDLs.
Waterkeeper and MEIC argue that the EPA had knowledge of these revisions when they submitted technical comments and expert reports highlighting flaws in the drafts in 2024 for DO and ammonia and early 2026 for pH. The 60-day notice serves as an official warning that if the EPA does not fulfill its duty to act upon Montana’s revised water quality standards, the groups will take the issue to federal court.